Plastic impregnated paper and method and apparatus for making same



Jan. 2, 1962 A. SACHER 3,015,577

PLASTIC IMPREZGNATED PAPER AND METHOD AND APPARATUS FOR MAKING SAME IFiled Aug. 4, 1958 I'IIIIIIIII 1 FIG.

:NVENTOR ALEX SACHER BY fi KMMCZ ATTORN EYS,

Patented Jan. *2, 1962 3,431.5,577 PLASTIC MPREGNATED PAPER AND METHGDAND APPARATUS FUR MAKING SAME Alex Sacher, Mapiewood, N..l., assignor,by mesne 3-) signments, to Standard insulation Company Inn, EastRutherford, P13... a corporation of Delaware Filed Aug. 4, 1958, Ser.No. 752,981 6 Claims. (1. 117-62) This invention relates to impregnatedpaper and particularly to paper impregnated with epoxy resins and to amethod and apparatus for impregnating paper.

The use of paper with business machines, such as data processingmachines and time clocks, has grown markedly in recent years. in thesetwo applications which are illustrative of other applications of paperwith business machines, the paper is usually in the form of a relativelystiff card. In data processing machines the card is usually providedwith a plurality of apertures which represent bits of information. Thepunched cards are passed through the machine and the apertures actuatecertain sensing devices to supply data to the machine for actionthereon. The tolerances for the passageway for the cards through suchdata processing machines must be relatively fine and, therefore, thecards themselves must be cut to precise dimensions and must havesubstantial dimensional stability so as to maintain said dimensions.

In automatic time clocks and the like, the cards are often subjected torough wear and for this reason they must be tough and not brittle.Furthermore, dimensional stability is also important for these cards astolerances in such apparatus are also quite fine. One of the most commonways for paper to vary its dimension is by way of swelling or shrinkingin response to variations in relative humidity. Particular difficultyhas been encountered in using cards of the type described in areas ofextremely high relative humidity. In such places the cards lose theirstiffness due to high moisture content and further swell to such anextent that they cannot be used in connection with their intendedapplication.

The main object of the present invention is to provide a new andimproved card or paper Which has extremely iine dimensional stabilityregardless of humidity conditions, which is tough enough to withstandrelatively hard handling, and which may be written and printed on withease.

Another object of the present invention is the pr vision of a newimproved epoxy resin impregnated paper.

Still another object of the present invention is the provision of a newand improved epoxy resin to serve as an impregnating agent for paper andthe like.

till ZDOtLST object of the present invention is the provision of a newand improved method of impregnating paper and the like with resin.

Yet a further object of the present invention is the provision of a newand improved method for impregnating paper and the like with epoxy resinwhich method results in a controlled moisture content for the finishedproduct.

Still another object of the present invention is the provision of newand improved apparatus for impregnatirx paper and the like with resin.

The above and other objects, characteristics and features of the presentinvention will be more fully understood from the following descriptiontaken in connection with the accompanying illustrative drawing.

in the drawing:

PEG. 1 is a dia rammatic vertical sectional view of apparatus forimpregnating paper with resin;

FIG. 2 is an enlarged detailed view illustrating means for controllingthe amount of resin in the paper being impregnated; and

FIG. 3 is an enlarged sectional view showing means for controlling theamount of water contained in impregnated paper.

Referring now to the drawing in detail the apparatus for impregnatingpaper and the like is generally designated in FIG. 1 by the referencenumeral 10. This apparatus includes a shaft 12 on which is rotativelymounted a roll of paper 14 which supplies paper 16 to the remainder ofthe apparatus. Paper 16 is passed over two guide rollers 18 and 20 andinto a container or pot 22 holding a resinous impregnating agent 24. Thenature of impregnating agent 24 will be described in detail as thisdescription proceeds. The paper passes around a roller 26 disposedwithin container 22 and thence directly upwardly past a scraping means27 here shown as being made up as a first set of knives 28 including twoofiset knives 36 and 33. From the scraping means 27, paper 16 passesinto a curing tower 40 wherein the impregnating agent is subjected tosuitable heat to cure the resin therein. After the resin in the paper 16has been cured, the paper is passed out of curing tower 40 directlyvertically downward into a container or pot 48 for Water 50. Disposedwithin the container 48 is a roller 52 around which the paper 16 passesto then pass upwardly out of the water 5i through a squeezing means 53made up of two ofiset cylindrical bars 54 and 56. From the squeezingmeans 53 paper 16 passes over two guide rollers 58 and 6t and thenceonto a roll of paper mounted on a shaft 64 driven by any suitable motormeans M.

While many types of papers are suitable for this application, Igenerally prefer bleached or unbleached sulphite or sulphate papers madeof northern or southern pine having a thickness of about 7 mils. Ipresently prefer to use bleached sulphite paper made of northern pine.Such papers are available in relatively large rolls, such as the roll 14rotatably mounted on shaft 12. As already stated, paper 16 is fed ofithe roll 14 and over two spaced guide rollers 18 and 20 and thence intoa container 22 for impregnating agent 24. Roller 26 which is disposed incontainer 22 is preferably totally immersed in the resin 24, here shownas being about an inch below the surface of the resin. With a resin ofthe type to be described hereinafter having a given viscosity and otherproperties, the immersion time of the paper in the resin is critical. Ihave found that a suitable impregnation is achieved without undue wasteof resin if the paper is immersed in the resin 24 for between about 1 /2and 3 seconds. For a relatively high linear speed of the paper of theorder of about 500 yards per hour, the duration of the immersion timecan best be controlled by the diameter of roller 26 and the depth of itsimmersion in resin 24. However, the diameter of the roller is criticalas if it is too small, the paper will crack or the pores will be openedtoo wide and thus cause the paper to take up too much resin, and if thediameter of roller 26 is too large, the pores will not be openedsulficiently Wide. I have found that the diameter of roller 26 should bebetween 2 /2 and 3 /2 inches, with 2 inches presently being preferred.With the roller 26 immersed to a depth of 1 inch below the surface ofresin 24 such a roller will yield an immersion time of about 1.66seconds for a linear speed of about 500 yards per hour. Paper 16 passesinto the resin 24 around the roller 26 and thence substantiallyvertically upward out of the container 22 past scraping means 27.

The knives making up scraping means 27 are supported in the positionshown in any suitable manner. The positioning of the knives is such asto scrape the surfaces of paper 16 so as to remove the excess of resinpicked up during the immersion of the paper in the resin 24. It is vitalto the present invention that the paper not contain an excess of resinas that would render the product difficult to print or write on. The twosets of knives 28 and 34 overcome this problem by forcing relativelysharp knife edges against the surfaces of paper .16 to scrape off anexcess of resin.

This scraping action is controlled by the positioning of the knivesrelative to one another and to the roller 26. preferably, the edge ofknife 30 is disposed one-half inch to the left of the rightmost elementof roller 26 and about one-half inch above the surface of resin 24. Theedge of knife 32 is approximately 1% inches above and 1% inches to theright of the edge of knife 30 whereby with the paper 16 being pulledsubstantially vertically upward, both surfaces of the paper 16 will bethoroughly scraped by the knife edges of knives 30 and 32. Knife set 34is about three inches above knife set 30 and the edges of knives 36 and38 are disposed relative to one another in substantially the exactpositions as knives 30 and 32, respectively. Such a positioning of theknives will result in the desired amount of resin 24 being left in thepaper 16 when the knives are about of an inch thick and have a throat ofabout /s of an inch and are disposed at an angle to the horizontalsomewhere between about and 30. The resin scraped off by the knives willflow down the knives away from the paper and ultimately drip back intocontainer 22.

After the impregnated paper has passed over the knives to effect ascraping and hence a removal of excess resin to bring the resin contentin the paper down to the desired amount of about 8% to 11% by weight,the paper is passed into the curing tower 40 to set the resin.

Curing tower 40 comprises a peripheral side wall 41 here shown asrectangular in configuration and a rectangular top or roof 43 whicheffectively closes the tower on all surfaces but the bottom. Disposedwithin tower 40 are a plurality of serpentine tubes 46 each tube windingin a vertical plane and being horizontally spaced from each other tube.The spaces in between the tubes 46 comprise passageways for the paper 16to pass upwardly and downwardly through the tower. In order to providefor the reversal of the direction of movement of paper 16, a pluralityof rollers 42 are provided adjacent the top of the tower 40 and anotherplurality of rollers 44 which are horizontally offset from the rollers42 are provided adjacent the bottom of tower 40. The tubes 46 areadapted to have super-heated steam passed therethrough in order to heatthe tower to a curing temperature for the resin 24. For the resin nowpreferred in the present invention, the temperature in the heating toweris controlled to between about 300 F. and 315 F. With this temperatureit has been found that a complete curing of the resin 24 can be effectedin about 14 minutes. Accordingly, if the paper is advanced throughapparatus at a rate of about 500 yards per hour, it will be seen that apath length of 120 yards through the tower will provide a curing time of14.4 minutes which is presently preferred. This governs the dimensionsof the curing tower and the only other factor which must be consideredis that the tower must be tall enough to provide suflicient curing ofthe resin 24 during the initial upward passage of the paper through thetower to prevent adhesion of the paper with the left-most roller 42.With the resin which is preferred in the present invention it has beenfound that suificient curing to prevent adhesion with the left-mostroller 42 can be effected in about 50 seconds. Accordingly, the heightof the tower should be about 7 /2 yards which will give the resin about54 seconds of heating prior to its initial engagement with a roller 42and thus prevent adhesion with said roller. Accordingly, as shown hereinthe tower is about 7 /2 yards high and is arranged to provide 8 upwardand 8 downward passes through the tower in order to effect the propercuring of the resin 24 in a path length through tower 40 of 120 yards.It will be understood that in lieu 4 of using pipes 46 for carryingsuper-heated steam to supply the necessary heat in tower 40 for curingresin 24 in paper 16, other suitable heating means may be employed suchas, for instance, electric heating elements and the like.

After the paper 16 passes vertically downwardly out of the tower itpasses into the container 48 for water 50. As set forth above, thehorizontal roller 52 is disposed within container 48 and is preferablyimmersed in the water, here shown to a depth of about 2 inches.

While the diameter of the roller 52 is not as critical as the diameterof the roller 26 discussed above, it too must not be of so small adiameter that the paper will be cracked when passing around it. l havefound that immersion time of the cured impregnated paper 16 in water 5'0is preferably between about 3 /2 and 4 /2 seconds and this can beachieved by employing a 6 inch diameter roller which is immersed to adepth of 2 inches below the surface of water. Such an arrangement willyield an immersion time in water 50 of about 3.8 seconds at a speed of500 yards per hour. The immersion of the impregnat ed paper in the waterpermits the paper to take up a substantial amount of water 50 and thus,after further treatment, as will be described hereinafter, to providethe finished paper with a suitable water content to reduce itssensitivity to variations in relative humidity. After paper 16 passesaround the roller 52, it is subjected to a squeezing action by the twohorizontally extending horizontally and vertically offset cylindricalbars 54 and 56 to remove the excess of Water in the paper. I have foundthat a proper squeezing can be effected by using bars with a inchdiameter which are offset at an angle of 45. The bars are biased towardseach other for squeezing action by any suitable means such as, forinstance, springs, elastic bands or the like. After passing between thesqueezing bars 54 and 56 the paper passes over the two additional guiderollers 58 and 60 and is then wound onto the rotating roll 62.

In accordance with one of the features of the present invention, afterthe roll 62 has been wound to desired size, it is removed from the shaft64 and placed in a substantially water impervious container and held insaid container for sufiicient time to permit the water in the paper toequally distribute itself throughout the roll. One extremelysatisfactory type of container is a plastic film such as, for instance,Saran which may be wrapped around the roll and which will act as anexcellent moisture barrier with a roll 62 having a diameter of about 24inches, a width between about 24 and 37 inches and a weight betweenabout 200 and 300 pounds; excellent moisture distribution is achievedwithin about 7 days of storage. The desired percentage of water isbetween 4 /2 and 5 A2 percent by weight of the finished product and thispercentage is readily achieved by the described method.

After the water distribution has been achieved, the paper may beunrolled from roll 62 and cut into desired shape.

While many resins may be employed as impregnating agents for paper, Ihave found that a superior product is obtained by impregnating the paperwith an epoxy resin. Preferably the impregnating agent 24 comprises fourcomponents. The first component is an epoxy resin which has beenpolymerized to a molecular weight between about 350 and 475, a viscosityof from about 4,000 to about 90,000 centipoises at about 73 F. and hasan epoxy equivalent of from about .44 to about .48 mol per grains. Tothe epoxy resin is added a flexibilizing agent in the form of a monomerhaving reactive epoxy groups. Such a monomer may be diagrammaticallyillustrated in the following manner:

where R is preferably an aliphatic radical. A cross linking agent in theform of an anhydride constitutes the third component of the impregnatingagent 24. Anhydrides suitable for use in the present application arethose having a side group taken from the class consisting of aromaticsand aliphatics containing 4 to 18 carbon atoms. The fourth component ofimpregnating agent 24 is a temperature latent amine catalyst. Bytemperature latent is meant a catalyst which will be effective as acatalyst only at elevated temperatures and will not be effective at roomtemperatures. This insures a good pot life for impregnating agent 24.

More specifically, impregnating agent 24 is composed of the condensationproduct of bis-phenol-A and epichlorhydrirl which has been polymerizedto a molecular weight of between 350 and 475, a viscosity of 4,000 to90,000 centipoises at about 73 F. and has an epoxy equivalent of about.44 to .48 mol per 100 grams. Most preferably the condensation productof bis-phenol-A and epichlorhydrin has an epoxy equivalent of .44 to .48mol per 100 grams, a molecular weight between about 420 and 460 and aviscosity between about 42,000 and 44,000 centipoises at 80 F. Such aresin may be purchased from the Ciba Company under the designationAraldite 6030. The preferred monomer for inclusion as a fiexibilizingagent is butyl glycidyl ether which may be purchased from the CibaCompany under the trade designation RDl. Considering that thecondensation product and the monomer together form the resin in theimpregnating agent 24, in order to achieve a final product having theproper flexibility, not too brittle and not tacky, the resin shouldconsist of about 50 to 90% of the condensation product and about to 50%of the monomer such as, for instance, butyl glycidyl ether. A crosslinking agent which I have found excellent for the present applicationis dodecynyl succinic anhydride and the anhydride should be present insufi'icient quantity to provide a ratio of epoxy groups in the resin toanhydride groups of about 1 to 1. The temperature latent amine catalystis preferably a tertiary or quaternary amine as such amines providelonger pot life than would a primary or secondary amine. One amine whichI have found to be extremely well suited for the present application istri-dimethyl amino-methyl phenol which may be purchased from Rohm andHaas under the designation DIVE-30. Again taking the condensationproduct and the monomer together as the resin in the impregnating agent,there should be about 1 to 2 parts of the amine catalyst for about every100 parts of the resin.

Cne excellent composition for impregnating agent 24 is composed asfollows:

Percent Condensation product of bis-phenol-A and epichlorhydrin havingan epoxy equivalent or" about .44

to .48 per 100 grams, a molecular Weight between 420 and 460 and aviscosity of 42,000 to 44,000

centipoises at 80 F. (Araldite 6030) 34 Butyl glycidyl ether (RDl) 21.5Dcdecynyl succinic anhydride 43.5 Tri-dimethyl amino-methyl phenol(DMP-30) 1 The viscosity of the above defined impregnating agentsimmediately after mixing same will generally be too low for immediateuse as the viscosity of the impregnating agent is relatively critical.If the viscosity is too low, there will be too much impregnation whichrender the final product difiicult to write on and have otherdeleterious efiects. if the viscosity of the impregnating agent is toohigh, it Will be difiicult to attain the desired degree of impregnationwhich is between 8% and 11% of plastic in the final product. It has beenfound that satisfactory results can be obtained if the viscosity of theimpregnating agent falls between 60 and 90 centipoises at 80 F, 80 F.being the temperature of the room in which the impregnating agent 24contained by container 22 is disposed. As the viscosity of the initialmixture is relatively low, and is generally Well below the lower limitof both the broad and narrow ranges of viscosity, it is necessary aftermixing the impregnating agent to let it stand for some time of the orderof about one and a half hours in order for the viscosity to be raisedinto the desired range preferably to 68 centipoises. As the process isworked, the viscosity of the impregnating agent in the pot 22 willcontinue to rise and it therefore becomes necessary to periodically addfresh (unaged) resin to maintain the viscosity in the desired range.This addition may be accomplished by adding to the pot 22 freshimpregnating agent that has been just mixed in a separate container orby having an automatic metering device which separately adds at desiredtime intervals or continuously, the proper amounts of the condensationproduct and monomer on the one hand and the anhydride and amine catalyston the other. By either expedient the viscosity of the impregnatingagent 24 can be closely controlled to yield an impregnating agent withthe desired characteristics.

The final product will be composed of paper having a substantiallyuniform distribution of cured impregnating agent and moisture. Theimpregnating agent will make up 8% to 11% of the finished product byweight and preferably about 9% and the moisture in the final productwill make up between about 4 /z% and 5 /2% of the final product andpreferably about 5%. If there is too little moisture in the finalproduct, it will be too brittle and it also will display a tendency toshred. If there is too much moisture,.it will be difiicult to punch andwill show a tendency to swell thus eliminating the desired dimensionalstability.

The final product of the type described hereinbefore is required to havea folding endurance of 300 and actually has an average folding enduranceof about 619. No fuzz is present on the surface. The expansion of a card3% inches by 7 /8 inches made from paper which has been processed in theabove described manner will be only about .19% in the longitudinaldirection and only about .7% in the transverse direction during a changein relative humidity from 20% to 75%. The contraction of such a cardduring a decrease in relative humidity of from 75% to 20% is only .22%in the longitudinal direction and .67% in the transverse direction.Moreover, such a card shows absolutely no warp. The coefficient ofstatic friction of a card made from paper processed as described abovemay be between .35 and .45 and actually is about .39 and the coefiicientof kinetic friction is the same. The stiffness of such a card asmeasured on a Tabor V-5 machine must be more than 18 in the longitudinaldirection and more than 8.5 in the transverse direction. Actualmeasurements show that a card made in accordance with the presentinvention has a stillness of 24 in the longitudinal direction and 11 inthe transverse direction. The bursting strength of the finished productis about 72 psi. and the thickness thereof is about 7.3 mils. Theaverage weight of 500 sheets 24 inches by 36 inches is about 101.1pounds.

With paper having the properties described above, excellent cards foruse in association with business machines can be made. Such cards may bereadily written and printed upon, roughly handled, subjected to widevariations in humidity Without failing to cooperate properly with theassociated machine. This highly desirable result stems from toughnes,dimensional stability, absence of warp and high folding strength of thedescribed product. Hence, highly reliable paper stock for use withbusiness machines is afforded by the present invention.

While I have herein shown and described the preferred embodiment of myinvention and have suggested various changes and modifications therein,other changes and modifications may be made therein within the scope ofthe appended claims without departing from the spirit and scope of thisinvention.

What is claimed is:

1. A plastic impregnated paper, said paper being taken from the groupconsisting of bleached and unbleached sulfite and sulfate papers ofnorthern and southern pine, said plastic being a fully polymerizedimpregnating agent,

said impregnating agent comprising a resin consisting es-.

sentially of about 50% to 90% of the condensation product ofbis-phenol-A and epichlorhydrin having an epoxy equivalent of from about.44 to about .48 mol per 100 grams and a viscosity of from about 4,000to about 90,000 centipoises at about 73 F., and about 10% to 50% of amonomer having reactive epoxy groups; said agent further comprising ananhydride having a side group taken from the class consisting ofaromatics and aliphatics containing 4 to 18 carbon atoms, said anhydridebeing present in such quantity as to provide an anhydride group to epoxygroup ratio of about 1:1; and about 1 to 2 parts of a temperature latentamine for about every 100 parts of said resin said plastic beingsubstantially uniformly distributed throughout said paper andconstituting from about 8% to 11% by weight of said impregnated paper,said plastic impregnated paper containing from about 4 /2 to 5 /2%water, this water being uniformly distributed throughout said paper.

2. A plastic impregnated paper, said paper being taken from the groupconsisting of bleached and unbleached sulfite and sulfate papers ofnorthern and southern pine, said plastic being a fully polymerizedimpregnating agent, said agent comprising a resin consisting essentiallyof about 50% to 90% of the condensation product of bisphenol-A andepichlorhydrin having an epoxy equivalent of from about .44 to about .48mol per 100 grams and a viscosity of from about 4,000 to about 90,000centipoises atabout 73 F., and butyl glycidyl ether; said impregnatingagent further comprising dodecinal succinic.

anhydride in such quantity as to provide an anhydride group to epoxygroup ratio of about 1:1; and about 1 to 2 parts of tri-dimethylamino-methyl phenol for about every 100 parts of said resin said plasticbeing substantial- 1y uniformly distributed throughout said paper andconstituting from about 8% to 11% by weight of said impregnated paper,said plastic impregnated paper containing from about 4 /2 to 5 /2 water,this water being uniformly distributed throughout said paper.

3. A plastic impregnated paper, said paper coming from the groupconsisting of bleached and unbleached sulfite and sulfate papers ofnorthern and southern pine,

said plastic being a fully polymerized impregnating agent,

said impregnating agent consisting essentially by weight of about 34% ofthe condensation product of bis-phenol- A and epichlorhydrin having anepoxy equivalent of about .44 to .48 mol per 100 grams and a viscosityof 42,000 to 44,000 centipoises at 80 F., about 21.5% butyl glycidylether, about 43.5% dodecinal succinic anhydride,

and about 1% tri-dimethyl amino-methyl phenol said plastic beingsubstantially uniformly distributed throughout said paper andconstituting from about 8% to 11% by weight of said impregnated paper,said plastic impregnated paper containing from about 4 /2 to 5 /2%Water, this water being uniformly distributed throughout said paper.

4. A plastic impregnated paper, said paper coming from the groupconsisting of bleached and unbleached sulfite and sulfate papers ofnorthern and southern pine, said plastic being a fully polymerizedimpregnating agent, said impregnating agent consisting essentially byweight of 8 about 34% of the condensation product of bis-phenol-A andepichlorhydrin having an epoxy equivalent of about? .44 to .48 mol per100 grams and a viscosity of 42,000 to 44,000 centipoises at F., about21.5% butyl glycidyl ether, about 43.5% dodecinal succinic anhydride,and about 1% tri-dimethyl amino-methyl phenol, said plastic beingsubstantially uniformly distributed throughout said paper andconstituting from about 8% to 11% by weight of said impregnated paper,said plastic impregnated paper containing from about 4 /2 to 5 /2percent water, this water being uniformly distributed throughout saidpaper.

5. The method of making plastic impregnated paper comprising immersing apaper selected from the group consisting of bleached and unbleachedsulfite and sulfate papers of northern and southern pine in a liquidimpregnating agent, said agent comprising (1) a resinous mixtureconsisting essentially of about 50 to of the condensation product ofbis-phenol-A and epichlorhydrin having an epoxy equivalent of from about.44 to .48 mol per grams and a viscosity of from about 4000 to 90,000centipoises at about 73 F., (2) about 10% to 50% of a monomer havingreactive epoxy groups, (3) an anhydride having side groups taken fromthe group consisting of aromatics and aliphatics containing from 4 to 18carbon atoms, said anhydride being present in such quantity as toprovide an anhydride group to epoxy group ratio of about 1:1 and (4)about 1 to 2 parts of a temperature latent amine for about 100 parts ofsaid resinous mixture, removing said paper from said impregnating agent,scraping both surfaces of said paper to remove excess impregnating agentuntil said impregnating agent constitutes from about 8 to 11% by weightof said impregnated paper, heating said scraped impregnated paper tocure the impregnatng agent therein, dipping said cured impregnated paperin water, and containing said wetted paper in a moisture imperviouscontainer until the water therein is substantially uniformly distributedand present in an amount equal to from 4 /2 to 5 /2% by weight of saidplastic impregnated paper.

6. The method of claim 5 wherein after said impregnated paper is dippedinto water the paper is subjected to squeezing to remove excess watertherefrom, this squeezing carried out prior to said step of containingsaid wetted paper in a moisture impervious container.

References Cited in the file of this patent UNITED STATES PATENTS2,049,978 Schur et al. Aug. 4, 1936 2,159,151 Hershberger May 23, 19392,365,621 Bender Dec. 19, 1944 2,373,849 Palmer Apr. 17, 1945 2,665,221Grangaard Jan. 5, 1954 2,716,074 Mick et al Aug. 23, 1955 2,768,153Shokal Oct. 23, 1956 2,837,497 Delmonte June 3, 1958 2,872,428 SchroederFeb. 3, 1959 OTHER REFERENCES Epoxy Resins, Henry Lee and Kris Neville,McGraw- Hill Book Co., Inc., New York, 1957.

1. A PLASTIC IMPREGNATED PAPER, SAID BEING TAKEN FROM THE GROUPCONSISTING OF BLEACHED AND UN BLEACHED SULFITE AND SULFATE PAPERS OFNORTHERN AND SOUTHERN PINE, SAID PLASTIC BEING A FULLY POLYMERIZEDIMPREGNATING AGENT SAID IMPREGNATING AGENT COMPFISING A RESIN CONSISTINGESSENTIALLY OF ABOUT 50% TO 90% OF THE CONDENSATION PRODUCT OFBIS-PHENOL-A AND EPICHLORHYDRIN HAVING AN EPOXY EQUIVALENT OF FROM ABOUT44 TO ABOUT .48 MOL PER 100 GRAMS AND A VISCOSITY OF FROM ABOUT 4,000 TOABOUT 90,000 CENTIPOISES AT ABOUT 73*F., AND ABOUT 10% TO 50% OF AMONOMER HAVING REACTIVE EPOXY GROUPS; SAID AGENT FURTHER COMPRISING ANANHYDRIDE HAVING A SIDE GROUP TAKEN FROM THE CLASS CONSISTING OFAROMATICS AND ALIPHATICS CONTAINING 4 TO 18 CARBON ATOMS, SAID ANHYDRIDEBEING PRESENT IN SUCH QUANTITY AS TO PROVIDE AN ANHYDRIDE BEING PRESENTIN GROUP RATIO OF ABOUT 1;1; AND ABOUT 1 TO 2 PARTS PF A TEMPERATURELATENT AMINE FOR ABOUT EVERY 100 PARTS OF SAID RESIN SAID PLASTIC BEINGSUBSTANTIALLY UNIFORMLY DISTRIBUTED THROUGHOUT SAID PAPER ANDCONSTITUTING FROM ABOUT 8% TO 11% BY WEIGHT OF SAID IMPREGNATED PAPERSAID PLASTIC IMPREGNATED PAPER CONTAINING FROM ABOUT 4 1/2 TO 5 1/2%WATER, THIS WATER BEING UNIFORMLY DISTRIBUTED THROUGHOUT SAID PAPER.